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Importance of the transition metal in the catalysis of a diene rearrangement
C42
Joumalof &gunometallic
ChemisOy
Ekevier Sequoia S.A., Lausanne Printed in The Netherlands
Preliminary communication Importance of the transition metal in the catalysis of a aiene rearrangement
ROY G. MILLER, PAUL A. PINKE, RICHARD D. STAUFFER and HARRY J. GOLDEN Chemistry Department, Universiq of North Dakota, Gmnd Forks, North Dakota 58201 (CL&j
(Received March 2nd, 1971)
We have observed that catalysts derived from the reaction of diisobutylahnninum chloride with trans-dichlorobis(trialkylphosphine)nickel(II) complexes skeletally rearrange 1,4-dienes’-3. A crucial factor in mechanistic studies of these transformations is the determination of the importance of^ the role of the transition metal component. We wish to report that some compounds of the general formula CzH4Ni(PR3)z, on combination with hydrogen chloride, afford extremely active catalysts for some of the same skeletal transformations as are provided by the catzlyst prepared in situ from nickel and aIuminum precursors_ Ethylenebis(tri-o-tolylphosphite)nickel(O) (I) was prepared by treatment of tris(tri-o-tolylphosphite)nickel(0)4 with ethylene 5~* _ The product could be crystallized from benzene-methanol at 0” to afford yellow crystals which exhibited a PMR spectrum (Cc,D6) in agreement with that of I’_ Treatment of a toluene solution of &s-l &hexadiene and I with hydrogen chloride at 25” (1 ,Qdiene/I/HCl mole ratio 12/l/0.65) resulted in a 37% conversion of the 1,4-diene to isomeric products during a 30 set period_ The isomeric product mixture consisted of trons-Zmethyl-1,3-pentadiene, 70%, rranwis-2,4&exadiene, lo%, cis,cis-2,4_hexadiene, 20%. Essentially 74% of the starting material had been converted to isomerie products within 2.5 minutes. Utilization of ethylenebis(triphenyIphosphine)nickel(O)* as the transition
metal component led to the generation of a somewhat less active catalyst after its treatment with HCl in the presence of &s-l &hexadiene (1,4diene/II/HCl 12/l .3/l -0). During 30 set, 19% of the 1,4diene was converted to products_ Of the material reacted, 80% was converted to an isomeric product mixture consisting of rrans-Z-methyl-1,3-pentadiene, 73%, trans,cis2,4hexadiene, 14%, and cis,cis-2,Phexadiene, 13%. The catalyst activity decreased rapidly with time, 31% of the cis-1,4-hexadiene being converted to products during 10 min and only a 49% conversion being reaiized during 4 hours. In similar experiments, both trans- and cis-2-methyIvinylcyclopropane* were rearranged by a combination of I and HCI to isomeric product mixtures which consisted of trans-Zmethyl-1,3-pentadiene and the geometric isomers of 2,4-hexadiene. In each case, *The compound was fust prepared by G. Wilkesb. %reparetby the procedure of Greaves et aL6a; the compound was first described by Wilke and Herrmanx . J. OrgrrnometaLChem, 29 (1971) C42-C44
PRELIMINARY
COMMUNICATION
C43
W3P&N'C2H4 HCI
I,
R=
-0
+
=z
2.4-Hexadienes
R=-@)
more than 60% of the starting material had been converted to-isomer& products wi.%in 6 minutes, Frans-Zmethyl-1,3pentadiene being the major product- The diene products in all of these reactions were isolated via preparative GLC and were identified by their PMR spectra. Control experiments demonstrated that neither HCl nor the nickel(O) complexes, alone, catalyzed the rearrangements at 29 when the same reactant concentrations were employed. The three 2,4_hexadiene geometric isomers were not isomerized by HCI, by II or by a l/l combination of HCl and II under the conditions described above. Treatment of each of the 2,4_hexadiene isomers with the catalyst derived from nickel and aluminmn precursors’ has also afforded no isomer&&ion. As was the case when EZZ~S-1,4_hexadiene was treated with the catalyst derived from nickel and aluminum precursors’, a l/l mixture
ofII
and HCI failed to cause its skeletal rearrangement, but afforded IJWZS,LWZSand trawcis-2,4_hexadienes as products. Treatment of II with an excess of HCl in the presence of c&l ,4-hexadiene provided an initial formation (during a few seconds) of small amounts of the isomerization products, followed by the rapid decomposition of the catalyst as evidenced by decolorization of the reaction mixture, deposition of solid material, and associated termination of diene isomerization. Precedent exists for the formation of hydridonickel compounds via the reaction of hydrogen acids with trialkylphosphine and trialkylphosphite complexes of nickel(O). The relatively stable chloro(hydrido)bisjtricyclohexylphosphine)nickel(iI) (III) has recently been synthesized and characterized ‘** . Gne of the routes for its preparation involved the addition of HCl to bis(tricyclohexylphosphine)nickel(O)’ _ The addition of hydrogen acids to tetrakis(triethylphosphite)nickel(O) has been shown to generate hydride complexes9 which catalyze double bond migration in alkenes” and the addition of alkenes to 1,3-dienes” . Compound III did not, however, catalyze the isomerization of c&l ,4hexadiene in toluene solution at 25”_ Also, the dichlorobis(tricyclohexylphosphine)nickeI(II)-diisobutylaluminum chloride system exhibited a very low activity for the isomerization of cis-1 +hexadiene_ Dichlorobis(triphenylphosphine)nickel(II) and diisobutylaluminum chloride afforded an active catalyst for the skeletal rearrangement only after ethylene was introduced to the reaction mixture. This “ethylene effect” on catalyst activity has been observed in other transformations’. The results demonstrate that the transition metal species plays a very significant role in the c&l ,Chexadiene rearrangement and that an aluminum component is not required_ They support the view that the catalyst is a nickel hydride or its chemical equivalent’**13 _
J Organometai them.,
29 (1971) C42-C44
044
pREUMINARY
COMHINXXTI~N
.. ACKNOWLEDGEMENT
AtzknbwIedgementis made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research. REFERENCES
1 RG. Miller,1. Amer. Chem Sot, 89 (1967) 2785. Miller and P.A. Pinke, J. Amer_Chem Sot, 90 (1968) 4500. 3 RG. Miller, P-A. Finke and D.J. Baker, 1 Amer. Chem Sot., 92 (1970)4490. 4 L.W. Gosser and C.A. Tohan,hzorg. Chem, 9 (1970) 2350. 5 (a)WK. Seidel and G.A. Tolman, Inorg. Chem, 9 (1970)2354; (b) G. Wilke,Atzgew. Chem Intern. Ed, 3 (1963) 10.5. 6 (a) E.O. Greaves, C.J.L. Lock and P.M. Maitlis, Con. J. Chem, 46 (1968) 3879; tb) G. Wilkeand G. Herrmann,Angw. Chem. 74 (1962) 693. 7 K. Jonasand G. Wilke, Angew..ChemIntern_Ed., 8 (1969)519. 2 RG.
8 9 10 11
M.L.H. Green and T. Saito, them Common., (1969) 208. CA. Tolman,J. Amer. Chem Sot., 92 (1970) 4217. R. Cramer and R.V. Lindsey, Jr., J. Amer. Chem Sot., 88 (1966) 3534. C-k Tohan,I. Amer. Chem Sot_, 92 (1970) 6777. See also, R.G. MilIer, T.J. Kealy and A-L. Barney, ibid, 89 (1967) 3756. 12 R Cramer, J. Amer. Chem Sot., 87 (1965) 4717. 13 F. Faraday, L. Bencze and L. Marko, /. OrgnnometnL Chem, 17 (1969) 107.
J. OrganometaL them, 29 (1971)C42-C44
Joumalof &gunometallic
ChemisOy
Ekevier Sequoia S.A., Lausanne Printed in The Netherlands
Preliminary communication Importance of the transition metal in the catalysis of a aiene rearrangement
ROY G. MILLER, PAUL A. PINKE, RICHARD D. STAUFFER and HARRY J. GOLDEN Chemistry Department, Universiq of North Dakota, Gmnd Forks, North Dakota 58201 (CL&j
(Received March 2nd, 1971)
We have observed that catalysts derived from the reaction of diisobutylahnninum chloride with trans-dichlorobis(trialkylphosphine)nickel(II) complexes skeletally rearrange 1,4-dienes’-3. A crucial factor in mechanistic studies of these transformations is the determination of the importance of^ the role of the transition metal component. We wish to report that some compounds of the general formula CzH4Ni(PR3)z, on combination with hydrogen chloride, afford extremely active catalysts for some of the same skeletal transformations as are provided by the catzlyst prepared in situ from nickel and aIuminum precursors_ Ethylenebis(tri-o-tolylphosphite)nickel(O) (I) was prepared by treatment of tris(tri-o-tolylphosphite)nickel(0)4 with ethylene 5~* _ The product could be crystallized from benzene-methanol at 0” to afford yellow crystals which exhibited a PMR spectrum (Cc,D6) in agreement with that of I’_ Treatment of a toluene solution of &s-l &hexadiene and I with hydrogen chloride at 25” (1 ,Qdiene/I/HCl mole ratio 12/l/0.65) resulted in a 37% conversion of the 1,4-diene to isomeric products during a 30 set period_ The isomeric product mixture consisted of trons-Zmethyl-1,3-pentadiene, 70%, rranwis-2,4&exadiene, lo%, cis,cis-2,4_hexadiene, 20%. Essentially 74% of the starting material had been converted to isomerie products within 2.5 minutes. Utilization of ethylenebis(triphenyIphosphine)nickel(O)* as the transition
metal component led to the generation of a somewhat less active catalyst after its treatment with HCl in the presence of &s-l &hexadiene (1,4diene/II/HCl 12/l .3/l -0). During 30 set, 19% of the 1,4diene was converted to products_ Of the material reacted, 80% was converted to an isomeric product mixture consisting of rrans-Z-methyl-1,3-pentadiene, 73%, trans,cis2,4hexadiene, 14%, and cis,cis-2,Phexadiene, 13%. The catalyst activity decreased rapidly with time, 31% of the cis-1,4-hexadiene being converted to products during 10 min and only a 49% conversion being reaiized during 4 hours. In similar experiments, both trans- and cis-2-methyIvinylcyclopropane* were rearranged by a combination of I and HCI to isomeric product mixtures which consisted of trans-Zmethyl-1,3-pentadiene and the geometric isomers of 2,4-hexadiene. In each case, *The compound was fust prepared by G. Wilkesb. %reparetby the procedure of Greaves et aL6a; the compound was first described by Wilke and Herrmanx . J. OrgrrnometaLChem, 29 (1971) C42-C44
PRELIMINARY
COMMUNICATION
C43
W3P&N'C2H4 HCI
I,
R=
-0
+
=z
2.4-Hexadienes
R=-@)
more than 60% of the starting material had been converted to-isomer& products wi.%in 6 minutes, Frans-Zmethyl-1,3pentadiene being the major product- The diene products in all of these reactions were isolated via preparative GLC and were identified by their PMR spectra. Control experiments demonstrated that neither HCl nor the nickel(O) complexes, alone, catalyzed the rearrangements at 29 when the same reactant concentrations were employed. The three 2,4_hexadiene geometric isomers were not isomerized by HCI, by II or by a l/l combination of HCl and II under the conditions described above. Treatment of each of the 2,4_hexadiene isomers with the catalyst derived from nickel and aluminmn precursors’ has also afforded no isomer&&ion. As was the case when EZZ~S-1,4_hexadiene was treated with the catalyst derived from nickel and aluminum precursors’, a l/l mixture
ofII
and HCI failed to cause its skeletal rearrangement, but afforded IJWZS,LWZSand trawcis-2,4_hexadienes as products. Treatment of II with an excess of HCl in the presence of c&l ,4-hexadiene provided an initial formation (during a few seconds) of small amounts of the isomerization products, followed by the rapid decomposition of the catalyst as evidenced by decolorization of the reaction mixture, deposition of solid material, and associated termination of diene isomerization. Precedent exists for the formation of hydridonickel compounds via the reaction of hydrogen acids with trialkylphosphine and trialkylphosphite complexes of nickel(O). The relatively stable chloro(hydrido)bisjtricyclohexylphosphine)nickel(iI) (III) has recently been synthesized and characterized ‘** . Gne of the routes for its preparation involved the addition of HCl to bis(tricyclohexylphosphine)nickel(O)’ _ The addition of hydrogen acids to tetrakis(triethylphosphite)nickel(O) has been shown to generate hydride complexes9 which catalyze double bond migration in alkenes” and the addition of alkenes to 1,3-dienes” . Compound III did not, however, catalyze the isomerization of c&l ,4hexadiene in toluene solution at 25”_ Also, the dichlorobis(tricyclohexylphosphine)nickeI(II)-diisobutylaluminum chloride system exhibited a very low activity for the isomerization of cis-1 +hexadiene_ Dichlorobis(triphenylphosphine)nickel(II) and diisobutylaluminum chloride afforded an active catalyst for the skeletal rearrangement only after ethylene was introduced to the reaction mixture. This “ethylene effect” on catalyst activity has been observed in other transformations’. The results demonstrate that the transition metal species plays a very significant role in the c&l ,Chexadiene rearrangement and that an aluminum component is not required_ They support the view that the catalyst is a nickel hydride or its chemical equivalent’**13 _
J Organometai them.,
29 (1971) C42-C44
044
pREUMINARY
COMHINXXTI~N
.. ACKNOWLEDGEMENT
AtzknbwIedgementis made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research. REFERENCES
1 RG. Miller,1. Amer. Chem Sot, 89 (1967) 2785. Miller and P.A. Pinke, J. Amer_Chem Sot, 90 (1968) 4500. 3 RG. Miller, P-A. Finke and D.J. Baker, 1 Amer. Chem Sot., 92 (1970)4490. 4 L.W. Gosser and C.A. Tohan,hzorg. Chem, 9 (1970) 2350. 5 (a)WK. Seidel and G.A. Tolman, Inorg. Chem, 9 (1970)2354; (b) G. Wilke,Atzgew. Chem Intern. Ed, 3 (1963) 10.5. 6 (a) E.O. Greaves, C.J.L. Lock and P.M. Maitlis, Con. J. Chem, 46 (1968) 3879; tb) G. Wilkeand G. Herrmann,Angw. Chem. 74 (1962) 693. 7 K. Jonasand G. Wilke, Angew..ChemIntern_Ed., 8 (1969)519. 2 RG.
8 9 10 11
M.L.H. Green and T. Saito, them Common., (1969) 208. CA. Tolman,J. Amer. Chem Sot., 92 (1970) 4217. R. Cramer and R.V. Lindsey, Jr., J. Amer. Chem Sot., 88 (1966) 3534. C-k Tohan,I. Amer. Chem Sot_, 92 (1970) 6777. See also, R.G. MilIer, T.J. Kealy and A-L. Barney, ibid, 89 (1967) 3756. 12 R Cramer, J. Amer. Chem Sot., 87 (1965) 4717. 13 F. Faraday, L. Bencze and L. Marko, /. OrgnnometnL Chem, 17 (1969) 107.
J. OrganometaL them, 29 (1971)C42-C44